A saw horse or trestle usually consists of two pairs of legs arranged more or less in the shape of a triangle, and a cross member extending between them. Such devices may be used for sawing lumber, or may be used in pairs or more for supporting a table surface.
It is a common experience that such articles must be transported from one work site to another, in order to provide a support for whatever work is being done at a particular location. For this purpose, it is clearly desirable that the support shall be collapsbile so that it occupies a small space, and can be transported easily. Similarly, it is clearly desirable that at the new work site it shall be capable of being readily erected without the use of tools to provide a rigid stable support.
Another factor in the design of such support is the variety of uses which may be required. Thus it may be desirable to provide at an upper level a support for a work surface such as a table, or some other device at about the height of the hip or waist of the workman. It may also be desirable to use the same device to provide a support at a lower level, for example, about the knee level of the workman to provide a stable surface on which to saw lumber.
Generally speaking, saw horses, trestles and the like in the past have provided only a single level of support, and thus have not been adaptable to the variety of different uses which may be required at any particular site.